Papermaking machine



Nov. 6, 1962 J. J. KRAUS ETAL PAPERMAKING MACHINE 5 Sheets-Sheet 1 FiledApril 15, 1959 Nov. 6, 1962 J. J. KRAUS ETAL 3,061,944

PAPERMAKING MACHINE Filed April 15, 1959 5 Sheets-Sheet 2 Nov; 6, 1962J. .1. KRAUS ETAL PAPERMAKING MACHINE Filed April .15, 1959 5Sheets-Sheet 4 3,%l,944 Patented Nov. 6, 1962 flee 3,061,944 PAPERMAKINGMACHINE James J. Kraus and Keith C. Martiny, Neenah, Wis, assignors toKimberly-Clark Corporation, Neenah, Wis, a corporation of Delaware FiledApr. 15, 1959, Ser. No. 806,653 12 Claims. (Cl. 34-110) The inventionrelates to pressure vessels and more particularly to welded wroughtdrier drums for use in the manufacture of paper.

A paper or tissue forming machine generally comprises a forming wirecarrying the wet paper web which is couched from the wire and ispartially dewatered between felts and which is subsequently pressed ontothe surface of at least one drier drum. These drums may be heated bymeans of steam applied internally of them. In the case of a so calledYankee type paper machine, only a single drum is used, and the wet paperweb is pressed onto the surface of the drum and is dried to the desiredfinal moisture content within a single revolution of the drum. TheYankee machine differs from the conventional Fourdrinier paper machinein that the latter has a number of small drier drums, and the paper istransferred from one drier drum subsequently to the others. The papermay be removed or creped from the large Yankee drier drum by means of adoctor blade which rides on the surface of the drum.

The present invention is concerned particularly with drier drums onwhich the doctor blade is applied and which distort substantially whenin use due to the steam pressure applied within them and due to thematerial of which the drum is constructed. Such distortion may beexpected to occur particularly when the drums are of a large size, beingof the Yankee type specifically, and particularly when the drums are ofwelded construction of high heat conducting material. Drier drums in thepast usually have been constructed of cast iron, and the doctor bladesin contact with them have been steel. With such drums of the Yankeetype, which may be of a diameter of 8 to 15 feet and a length of tofeet, there is some distortion due to the fact that the wet paper Web isnot applied for the complete width of the drum but only within a fewinches of each drum edge, and the wet paper web maintains the part ofthe drum with which it contacts at a lower temperature than thetemperature of the outer edges of the drum surface and the internalsurfaces of the drum. Cast iron and steel are somewhat compatible whenthere is rubbing action between the two materials, there being a slightlubricating action between them, and furthermore the cast iron does nothave a high coefficient of thermo-expansion as does other materialswhich are now proposed for use in drier drums; and consequently thewearing of cast iron drums by steel doctor blades has been uniformenough over the complete drum length as to be no major source oftrouble.

It has now been proposed to make the cylindrical drum surface of weldedsheets, preferably with the welds eX- tending diagonally with respect tothe axis of the drum, such as proposed in the application of C. G. R.Johnson, for Paper Making Machine, Serial No. 699,704, filed November29, 1957. In general, the Welds are more brittle than are the sheets,and hence the welds have been placed diagonally, so that the doctorblade is continuously in contact with at least one of the welds, forminimizing wear. It has been proposed to manufacture the drum of analuminum bronze, with both the metal sheets and also the welds being ofthis material. Aluminum bronze is softer than cast iron but transmitsmore heat than does cast iron, rendering it particularly suitable fromthe latter standpoint for drier drum usage. As with other metals,however, the aluminum bronze sheets are less brittle than the welds, andit has been found in actual usage of a drum of this construction that,even though the welds are diagonally disposed, nevertheless there hasbeen substantially and non-uniform wear of the drum due to the action ofthe doctor blade riding in contact with the drum. This wear has occurredparticularly at the outer edges of the drum behind the welds in theareas which do not carry the paper web. Such undue Wear does not occuron the drum surface carrying the paper sheets due apparently to thepaper debris that is carried by the drum in these areas over which thepaper web extends and due apparently also to the fact that the paper webin being creped from the drum has the action of tending to separate thedoctor blade from its contact with the drum.

It is therefore an object of the present invention to provide animproved drier drum construction minimizing such wear occurring on theouter edges of the drum.

Concisely, the invention comprises in providing areas of material harderthan the sheets, of which the drum surface is composed, on the outeredges of the drum surface; so that the doctor blade does not dig intothe drum to such an extent as to cause uneven wear of the drum on itsouter edges, outside of the drum areas on which the paper Web isdisposed.

The invention consists of the novel constructions, ar rangements anddevices to be hereinafter described and claimed for carrying out theabove stated objects and such other objects as Will be apparent from thefollowing description of preferred forms of the invention, illustratedwith reference to the accompanying drawings, wherein:

FIG. 1 is a fragmentary side elevational view of a paper machineincorporating a drier drum embodying the principles of the presentinvention;

FIG. 2 is a fragmentary end view on an enlarged scale of the drier drumas shown in FIG. 1;

FIG. 3 is a longitudinal sectional view on a reduced scale of the drierdrum;

FIG. 4 is a top plan View of a plate from which the drier drum isfabricated showing the cutting of the plate into two segments;

FIG. 5 is a view similar to FIG. 4 showing two plate segments weldedtogether to form a parallelogram shaped section;

FIG. 6 is a view similar to FIG. 4 showing the sections welded togetherto form the plate pattern;

FIG. 7 is a perspective view of the completed welded shell;

FIG. 8 is a diagram showing the crowning of the drier drum under twodifferent conditions;

FIG. 9 is a sectional view taken on line 9-9 of FIG. 2;

FIG. 10 is a sectional view similar to FIG. 9 of a modified form of drumstructure;

FIG. 11 is a side view of another modified form of drum structure; and

FIG. 12 is a side view of still another modified form of drum structure.

Like characters of reference designate like parts in the several views.

Referring now to the drawings and in particular to FIGS. 1 and 2, thereis illustrated fragmentarily a typical Yankee type paper machine,particularly the dry end of the machine, which includes a drier drum itThe drum is supported by a supporting frame 11 resting on a suit ablefoundation 12;. The wet paper web 13 is adapted to be applied to theouter surface of the drum having its edges 14 spaced a few inches fromthe edges of the drum and being dried by the drum during a singlerevolution thereof.

The drum It includes a generally cylindrical, welded shell 15 having endflanges 16 which are bolted to heads 3 17. The heads 17 enclose the endsof the shell and are provided with aligned axial openings which receivea hollow shaft 18.

The drum is mounted for rotation by providing the ends of the shafts 18with journals 19 which are rotatably disposed in bearings 20 secured tothe frame 11. The shaft 18 is formed of two hollow axially alignedsections 21 and 22 which are separated by a separator plate 23. Theseparator plate 23 is provided with a thickened rim 24, and a series ofopenings 25 extend through the rim and communicate with the interior ofthe shell 15. Steam nozzles 26 are threaded into the openings 25 andserve to distribute steam from the interior cavity 27 of the shaftsection 21 of the interior cavity 28 of the drum 10.

For removing steam condensate from the drum 10, a pair of scoops 29 aresecured to the ends of pipes 30 which extend radially through openings31 in the shaft section 22.

The drum 10 is rotated by a conventional driving mechanism (not shown)which is attached to the end of the shaft 18 by a suitable gear orpulley arrangement.

For providing additional heat to dry the paper Web on the surface of thedrum 10, a heated hood 32 is secured to the frame 11 and extends aroundthe upper portion of the drum 10. Suitable hot air inlets and outletsare provided in the hood for the entry and discharge of the air or otherheating medium.

The wet paper web to be dried is carried by a felt web 33 which travelsaround rolls 34. The paper web is forced against the surface of the drum10 by a pressure roller 35 which is rotatably mounted in brackets 36attached to an arm 37. The arm 37 is pivoted at 38 to the frame 11, andthe pressure roller 35 is forced against the surface of the drum '10 bya ram 39 of a hydraulic cylinder 40 which bears against the arm 37. Thedried paper web is removed from the surface of the drier shell by acreping doctor which includes a doctor blade 41 which is removablysecured from within a doctor blade holder 42. The ends of the holder 42are provided with shafts 43 which are rotatably mounted from withinguide blocks 44. The blocks 44 in turn are each mounted within a slideassembly 45 attached to a pivot frame 46 pivotally carried by frame 11.The doctor blade holder 42 and the blade 41 are pivoted by a togglemechanism 47 which is attached through a lever arm 48 to one of theshafts 43. In addition, a spring loading mechanism 49 of any suitabledetailed construction is connected through the toggle mechanism 47 toprovide a resilient contact for the doctor blade 41 against the surfaceof the drier drum 10.

In addition to the vertical and pivotal adjustment for the doctor blade41, the doctor blade is adapted to oscillate in a direction parallel tothe axis of the drum 10. The oscillating motion is provided by aneccentric drive which is shown generally at 50 connected to one of theshafts 43. The oscillating motion is permitted by a loose fit betweenthe pivot frame 46 and the frame 11 and permits the doctor blade to moveback and forth across the surface of the drum 10 as the drum 10 rotatesto prevent uneven wear of the blade 41.

The drum shell 15 is fabricated from a series of generally rectangularrolled plates 51. As shown in FIG. 4, the rectangular plates 51 areinitially cut diagonally at 52 to provide two halves or segments 53 and54. The cut at 52 is made so as to divide the rectangular plate 51 intotwo generally equal parts of similar shape and surface area. Aftersevering the rectangular plates into the parts 53 and 54, the edges ofthe segments are scarfed for welding, and the segments are reversed inposition so that the square ends are in abuttnig relation. The alignedends of the segments are welded together at 55 to provide a generallyparallelogram shaped section 56 as seen in FIG. 5.

A series of the parallelogram shaped sections 56 are then arranged withthe diagonal edges in alignment and the longitudinal side edges inopposed relation as shown in FIG. 6 to form a larger plate section. Theabutting side edges of the sections 56 are then welded together as at57, and the large parallelogram shaped pattern as seen in FIG. 6 is thenrolled into cylinder form, and the free ends are welded along line 58 toprovide the generally cylindrical welded structure shown in FIG. 7constituting the drum shell 15.

The plates 51 and also the other parts of the drum including the shaft18 and the heads 17 are preferably formed of an aluminum bronze alloywhich may have the specific compositions and which may be made inaccordance with the metallurgical processes described in the co-pendingapplication of John F, Klement, for A Welded Wrought Aluminum BronzeArticle and a Method of Heat Treating the Same, Serial No. 682,577,filed September 9, 1957. In brief, the alloy may contain 5 to 8 percentof aluminum, .05 to 4 percent of iron, .01 to 5 percent of nickel, .01to 5 percent of manganese, .01 to 2 percent of tin, .01 to 5 percent ofzinc and the balance of copper. The composition of the welding materialis substantially the same as the plates 51, having, however, a slightlygreater amount of aluminum, such as 8 percent to 11 percent, in view ofthe fact that a small amount of aluminum is lost during the weldingprocedure. The plates 51 are wrought, that is, rolled; while the otherparts of the drum 10 are cast.

The angle of the cuts 52 with respect to the longitudinal side edges ofthe plates 51 is greater than 5 degrees and preferably within the rangeof 30 degrees to 60 degrees, so that the welds 57, 55 and 58 extend atsubstantial angles with respect to the axis of the shell 15.

After the shell 15 has been rolled into its cylindrical form as shown inFIG. 7, it is heat treated to minimize the difierences in mechanicalproperties between the plates and the weld seams; and the shell 15 isslightly crowned, preferably on the order of .03 inch diameter for adrum 12 feet in length and over all diameter, that is, the drum has adiameter at its center .03 inch greater than on its edges and hassubstantially the form as shown by curve A in FIG. 8. This curve showsthe lengthwise contour of the shell surface 15 from the center of thedrum to one end, and the ordinates in this figure show the crowning fora certain drum embodiment of .015 inch on a radius, with the operatingsteam pressure being supplied to the internal cavity 28 of the drum 10and without a paper sheet on the drum to be dried thereby, so that thedrum 10 is at a uniform temperature throughout.

In operation, the paper web is disposed on the lower surface of thelower pass of the felt 33 and travels with the web 13 around the lowerfelt roll 34 to the pressure roller 35. At the pressure roll 35, thepaper web transfers from the felt Web 33 onto the outer surface of thedrum 10 and rotates with the drum 10 within the heating hood 32, so thatthe paper web is substantially completely dried by the time it reachesthe doctor blade 41 from its damp condition at its point of applicationat the pressure roll 35 to the outer surface of the drum 10.

The doctor blade 41 scrapes or crepes the paper web from the exteriorsurface of the drum 10, and the paper web is then rolled on suitablerolls (not shown) for storage purposes. For securing the correctpressure of application of the doctor blade 41 on the drum surface 15,the spring loading mechanism 49 may be manually adjusted.

In view of the fact that the welds 55, 57 and 58 extend at angles to thelongitudinal axis of the drum 10, the doctor blade 41 rides over atleast one of the welds at all times and does not pass from any of thewelds at a single instant so as to render uniform as possible any wearof the drum 10 caused by the doctor blade 41. Although the welds 57, 58and 55 are made with substantially the same alloy as is used for theplates 51, nevertheless, since the sheets 51 are wrought or rolled whilethe welds are in the nature of castings, actually the welds have longerwear characteristics than does the outer drum shell 15 under doctorblade scraping action, being in general slightly more brittle and hard.Therefore, if the outer shell 15 were made with welds extendinglongitudinally on the shell, it could be expected that the doctor blade41 would wear longitudinal grooves in the shell 15 just in back of thewelds. This action has in general been avoided due to the diagonallyextending welds. However, in actual usage of the drum as shown in FIG.7, without the surface treatment of the shell to be subsequentlydescribed, it has been found that slight depressions 59 (see FIG. 2)have been worn in the outer surface of the drum it between the edges 14of the paper web and the outer edges of the drum, due to the action ofthe doctor blade 41, these depressions being immediately behind thewelds 57 and 58. No such wear behind the welds 57 and 58 has beennoticed in the portion of the shell covered by the paper web, dueapparently to the paper debris that collects to a slight extent on thisportion of the drum It) and which apparently functions as a slightlubricant. Although this wearing could be expected to a slight extent ifthe shell 15 were made of plates of iron or any other relatively hardmaterial welded together, nevertheless, the aluminum bronze alloy whichis preferred for its heat conducting qualities is somewhat softer, andthis wearing action therefore may be expected to be noticeable in thiscase. Such wear is objectionable for a number of reasons, including,weakening of the drum against the pressure of the steam used for heatingit.

Referring to FIG. 8, the curve A, as previously mentioned, shows thecrowning of a certain drier drum that exists when the drier drum isunder operating steam pressure. Curve B in FIG. 8 shows the lengthwisecontour of the drum when the drier drum is in use with a paper web beingdried by the drum. Curve B shows that there are high points 611 in thedrum existing nearly at the edges 14 of the paper web which would causethe doctor blade 41 to tend to dig into the exterior surface of the drumat these points. The change in diameter and change in shape of the shell15 is caused by the reduction in temperature of the shell 15 between theedges 14 of the paper web due to the evaporation from the web. Thesurface of the shell 15 between its edges and the paper web edges 14,the other parts of the drum 10 including the heads 17 and shaft 18, asWell as the internal surface of the shell 15, remain at the hightemperature of the steam pressure. The reduction in average temperatureof the shell 15- between the paper web edges 14 results in a reductionin diameter and a slight reduction in length of this portion of theshell 15, with the peripheral edges of the heads 17 drawn inwardlyslightly, thus causing the inwardly bowed shape of the shell indicatedby the curve B, with high points an adjacent the drum edges. When thedrum is made out of aluminum bronze as previously described, the highpoints 6% are more pronounced than with a cast iron drum, for example,since the temperature coeflicient of expansion is different for thealuminum bronze material as compared to cast iron, and for this reasonthere tends to be a greater abrasive effect of the doctor blade adjacentthe edges of the drum. In addition, the aluminum bronze alloy is softerthan cast iron, and although having the advantage of transmitting heatbetter than cast iron, nevertheless is more prone to be damaged by thescraping action of the doctor blade 41. The aluminum bronze alloy alsodoes not provide the same high lubricating eifect with re spect to thesteel doctor blade 41 that is provided by the cast iron. Thus, wearbetween the edges 14 of the paper web and the edges of the drum occurswith usage of the drum if the drum is made of the aluminum bronze alloyrather than of cast iron, the wear concentrating in regions 59 behindthe welds 57 and 58 if the aluminum bronze drum 10 is of the weldedconstruction, as illustrated.

In order to overcome the scraping action of the doctor blade 41 on thesurface of the welded aluminum bronze drum 15, the present inventioncontemplates the pr0vision of a plurality of circular bands 61 extendingaround the drum 1t) and indented in the surface of the drum. These bandsmay be of any longer wearing or harder material than that of the drumsurface under doctor blade scraping action, and may be simply bands ofthe welding material either sprayed or welded into circumferentialgrooves 62. Other harder metals such as chromium can also be used. Thesebands may be 1 inch to /2 inch in thickness but on the other hand can bemade much thinner if desired, such as 32 inch thick. The bands 61prevent the doctor blade 41 from scraping off the surface of thealuminum bronze drum between the edges 14 of the paper web and the edgesof the drum, effectively holding the doctor blade at the surface of theshell 15 and preventing the formation of the depressions 59.

The grooves 62 are preferably formed in the drum 15 after it has beenrolled into cylindrical form but in certain instances it may be founddesirable to form the grooves 62 in the assembled plate structure asillustrated in FIG- URE 6 and to fill those grooves with the weld orother metal prior to the forming of the cylinder. The procedure willresult in certain instances in the rings 61 having a physical structurewhich more closely approximates the main body of the cylinder or whichmay have desired differing characteristics.

As an alternative to providing the circumferential rings 61 on the endsof the drum 10, cylindrical rings 63 (see FIG. 10*) may be provided onthe ends of the drum. The rings 63 may be of the same longer wearing orharder material as the rings 61 and are provided in grooves 64 on theends of the drum. The cylindrical rings 63 may be either sprayed orwelded of the aluminum bronze weld material, for example, within thegrooves 64 or may he slipped on to the drum from its ends.

As another alternative, the drum 10 may have a cylindrical shell 65provided over its complete exterior as shown in FIG. 11. The shell 65may be of the aluminum bronze weld material, or the shell 65 may simplycomprise a plating, such as of chromium, for example. The weld materialmay be welded on the outer surface of the drum, if desired, and theplating may be applied by conventional plating methods or by metalizingprocesses in which the metal is sprayed on. When an outer cylindricalshell 65 is provided, the plates 51 may be of heat conducting materialsother than the aluminum bronze alloy previously mentioned (such asiron); and the shell 65, if of the aluminum bronze weld material,provides the same good wearing qualities as previously mentioneduniformly over the complete outer surface of the drum. In the event thecomplete cylindrical shell 65 is used, the drum 19 in this case may beformed of sectors 66 of rolled strips of the aluminum bronze metalhaving welded joints 67 extending parallel to the axis of the drum (seeFIG. 12).

The rings 61 advantageously prevent the undue wearing of the edges ofthe drum 1!). Furthermore, the rings are relatively inexpensive to applyand are effectively held in position by the surrounding portions of theshell 15 forming the grooves 62. The cylindrical rings 63, althoughperhaps being more difficult to apply and fasten to the drum, assurethat the complete edge surfaces of the shell 15 subject to the abradingeifect of the doctor blade 41 are protected. The cylindrical shell 65,although perhaps distracting to some extent from the heat transmittingqualities of the drum as a whole, assuming that the shell 65 is of somebaser material than the shell 15, nevertheless assures that the abradingeffect of the doctor blade 41 is substantially the same over thecomplete surface of the drum 10.

It is to be understood that the invention is not to be limited to thespecific constructions and arrangements shown and described, except onlyinsofar as the claims may be so limited, as it will be understood tothose skilled in the art that changes may be made without departing fromthe principles of the invention.

What is claimed is:

1. In a papermaking machine drier drum for use with a doctor bladeadapted to bear on the drum and to scrape paper Web from the drum, agenerally cylindrical rotatable drier shell adapted to receive a Web ofwet paper on the outer surface thereof and dry the Web as the shell isrotated, said shell comprising a plurality of curved plates of heatconducting relatively soft metal welded together to form the shell,circumferential ring portions of the outer surface of said shell onopposite ends of the shell being covered by protective layers of arelatively hard metal, the outer surfaces of which are flush with theouter surface of said shell, for preventing a doctor blade in scrapingrelation with said shell from gouging out the surface of said shelladjacent its outer edges.

2. In a papermaking machine, a rotatable drier drum, a doctor bladebearing on the drum to scrape paper web from the drum, said drumcomprising a generally cylindrical drier shell of a relatively softmaterial adapted to receive a web of wet paper on the outer surfacethereof and to dry the Web as the shell is rotated, and a ring portionof a material harder than said first named material and disposed on eachend of said shell to be flush with the outer surface of the shell forpreventing the doctor blade in scraping relation with said shell fromgouging out the surface of said shell adjacent its outer edges.

3. In a papermaking machine drier drum for use with a doctor bladeadapted to bear on the drum and scrape paper web from the drum, agenerally cylindrical rotatable drier shell adapted to receive a web ofwet paper on the outer surface thereof and dry the web as the shell isrotated, said shell comprising a plurality of curved plates of a heatconducting relatively soft metal welded together forming the shell, anda ring portion of a material harder than said metal and disposed on eachend of said shell to be flush with the outer surface of the shell forpreventing a doctor blade in scraping relation with said shell fromgouging out the surface of shell adjacent its outer edges.

4. In a papermaking machine drier drum for use with a doctor bladeadapted to bear on the drum and scrape paper web from the drum, agenerally cylindrical rotatable drier shell adapted to receive a web ofwet paper on the outer surface thereof and dry the web as the shell isrotated, said shell comprising a plurality of curved plates of a bronzemetal welded together forming the shell, and a ring portion of a metalharder than said bronze and disposed on each end of said shell to beflush with the outer surface of the shell for preventing a doctor bladein scraping relation with said shell from gouging out the surface ofsaid shell adjacent its outer edges.

5. In a papermaking machine drier drum for use with a doctor bladeadapted to bear on the drum and scrape paper web from the drum, agenerally cylindrical rotatable drier shell adapted to receive a web ofwet paper on the outer surface thereof and dry the web as the shell isrotated, said shell comprising a plurality of curved plates weldedtogether at their edges to form the shell, said curved plates being ofsuch shape that their welded edges extend diagonally with respect to theaxis of the shell, and a plurality of rings of a material harder thanthe material of said plates and indented within said shell at each endof the shell to be flush with the outer surface of the shell forpreventing a doctor blade in scraping relation with the shell fromgouging out the surface of the shell adjacent its outer edges.

6. In a papermaking machine drier drum for use with a doctor bladeadapted to bear on the drum and scrape paper web from the drum, agenerally cylindrical rotatable drier shell adapted to receive a web ofwet paper on the outer surface thereof and dry the web as the shell isrotated, said shell comprising a plurality of curved plates weldedtogether at their edges to form the shell, said curved plates being ofsuch shape that their welded edges extend diagonally with respect to theaxis of the shell, and a cylindrical band portion of a material harderthan the material from which said plates are formed and disposed on eachend of said shell to be flush with the outer surface of the shell forpreventing a doctor blade in scraping relation with the shell fromgouging out the surface of the shell adjacent its outer edges.

7. In a papermaking machine drier drum for use with a doctor bladeadapted to bear on the drum and scrape paper web from the drum, agenerally cylindrical rotatable drier shell adapted to receive a Web ofwet paper on the outer surface thereof and dry the web as the shell isrotated, said shell comprising a plurality of curved plates weldedtogether at their edges to form the shell, said curved plates being ofsuch shape that their welded edges extend diagonally with respect to theaxis of the shell, and a cylindrical band of a material harder than thematerial of said plates and disposed on each end of said shell inindented relation with respect to the outer surface of the shell to beflush with the outer surface of the shell for preventing a doctor bladein scraping relation with the shell from gouging out the surface of theshell adjacent its outer edges.

8. In a paper machine drier drum for use with a doctor blade adapted tobear on the drum and scrape paper web from the drum including agenerally cylindrical drier shell adapted to receive a web of wet paperon the outer surface thereof and to dry the web as the shell is rotated,said shell comprising a plurality of curved plates of a bronze alloywelded together to form the shell with the welded edges of the platesextending diagonally of the axis of the shell, the improvement whichcomprises a ring portion of a material harder than said bronze alloy andindented in the outer surface of the shell on each end of the shell tohave its outer surface flush with the outer surface of the shell forpreventing the doctor blade in scraping relation with the shell fromgouging out the surface of the shell adjacent its outer edges.

9. A papermaking machine drier drum comprising a generally cylindricaldrier shell which is made up of a plurality of curved plates of a bronzemetal welded together forming the shell, and a ring portion of a metalharder than said bronze and indented in the shell on each end of theshell to be flush with the central portion of the shell.

10. In a papermaking machine drier drum for use with a doctor bladeadapted to bear on the drum and to scrape paper web from the drum, agenerally cylindrical rotatable drier shell of a relatively softmaterial adapted to receive a web of wet paper on the outer surfacethereof and to dry the web as the shell is rotated, and a ring portionof a material harder than said first named material and indented in saidshell on each end thereof within grooves provided in the shell so as tobe flush with the outer surface of the shell for preventing a doctorblade in scraping relation with the shell from gouging out the surfaceof the shell adjacent its outer edges.

11. In a papermalting machine, a rotatable drier drum comprising agenerally cylindrical drier shell of a relatively soft material adaptedto receive a web of wet paper on the outer surface thereof and to drythe web as the shell is rotated, a doctor blade bearing on the drum forscraping paper web from the drum, means for admitting heating fluid intothe drum for heating the drum, means for removing said heating fluidfrom the drum for providing circulation of heating fluid through thedrum, and a ring portion of material harder than said first namedmaterial and indented within said shell on each end of the shell so asto be fiush with the central portion of the shell for preventing thedoctor blade in scraping relation with the shell from gouging out thesurface of the shell adjacent the edges of the shell and the edges ofthe paper web.

shell comprising a plurality of curved plates of a heat 10 conductingrelatively soft metal welded together forming the shell, and a ringportion of a material harder than said metal and indented within saidshell on each end of the shell to be flush with the central portion ofthe shell for preventing the doctor blade in scraping relation 15 1 0with the shell from gouging out the surface of the shell adjacent itsouter edges and adjacent the edges of the paper web in the vicinity ofthe welds.

References (Iited in the file of this patent UNITED STATES PATENTS1,763,629 Hopkins June 10, 1930 2,047,372 Jalens July 14, 1936 2,141,377Chylinski Dec. 27, 1938 2,151,048 Rowe Mar. 21, 1939 2,653,061 Lewis eta1 Sept. 22, 1953 FOREIGN PATENTS 692,215 Great Britain June 3, 1953UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Noo 8 O61944 November 6 1962 James Jo Kraus et alo or appears in the abovenumbered pat- It is hereby certified that err d Letters Patent shouldread as ent requiring correction and that the sai corrected below.

Column 3 line 14; for "of first occurrence read to g llne 7O for"abuttnig" read abutting -=s Signed and sealed this 28th day of May19630 ISEAL) Attest:

DAVID L. LADD Commissioner of Patents ERNEST W. SWIDER Attesting Officer

